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Lecture 6

PSYCH 9A Lecture Notes - Lecture 6: Absolute Threshold, Normal-Form Game, Tabula Rasa


Department
Psychology
Course Code
PSYCH 9A
Professor
Bruce Berg
Lecture
6

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PSYCH 11A - LECTURE 6
SENSATION (PART I)
!
ORIGIN OF KNOWLEDGE
-EMPIRICISM - knowledge is acquired through experience (nurture).
-John Locke - when born, the mind is blank, a “tabula rasa” (blank tablet).
-Experience refers to working with the information provided to us by our senses and other faculties like
memory.
-Basic Distinction:
-Distal stimulus - an object or event in the outside world., like a person (what we want).
-Proximal stimulus - the energy from the outside world that directly reach our sense organs, such as the
light from the person reaching to our eyes (what we get).
-Problem: the proximal stimulus does not tell us directly what the distal stimulus is.
-Example: We hear someone speaking and want to know what she’s saying - distal stimulus, sound-
pressure waves arriving to our eardrums - proximal stimulus.
-Proximal image size does not directly tell us how big the real-world distal stimulus is.
-Example: Consider how the size of a visual image of some objects depends on viewing distance
(retinal-image size - proximal stimulus, cannot tell us the size of distant object - distal stimulus).
-George Berkeley - two stages are needed to understand how the mind works to interpret proximal
stimuli.
-Our senses provide raw input - sensations (proximal stimulus).
-E.g: patch of green, a note on a piano, a salty taste, touch of a feather.
-Our minds link these sensations to provide a meaningful organization of our perceived world:
associations (through depth cues contained within the retinal image).
-E.g: a spherical patch of green above a cylindrical patch of brown, a tree.
-NATIVISM - knowledge is innate (nature)
-Immanual Kant:
-Categories according to which sensory material is organized:
-Space (dimensions), time (direction), and causality (causility) are “a priori” (built-in or innate).
-Experience provides sensory input ordered according to the “a priori” categories.
!
PSYCHOPHYSICS
-Relates characteristics of a proximal stimulus to the quality and intensity of its sensory experience.
-DETECTION (important distinction).
-Absolute threshold - the smallest quantity of a stimulus
that an individual can detect.
-What is the smallest amount of light that you can detect
if view in an otherwise completely dark room?
-What is the intensity of the faintest sound you can hear?
-Difference threshold - the smallest amount that a given
(physical) stimulus must be differed so that an individual
can detect the difference.
-What is the smallest amount that two lights can differ in
physical intensity and still differ in perceived brightness?
-How much change in sound frequency is needed for you
to tell the difference between a 256 Hz tone (middle C on a piano) and a tone of higher frequency?
-DISCRIMINATION:
-Tell two stimuli apart.
-If the physical difference between two stimuli is as small as possible for us to tell two stimuli apart, then we
are measuring a difference threshold.
-The difference threshold corresponds to a just noticeable difference (JND) - the smallest difference that an
organism can reliably detect between two stimuli.
-In the standard experiment, one compares a test or comparison stimulus to the standard or reference
stimulus.
*Difference thresholds depend on proportional differences and not absolute differences.
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